Not sure, mainly because I've never done it.
But I just wanted to say that they may well eat the wood chips, at least for a while. I've found that they try to eat loads of inappropriate things that are not food. Watch what happens next time you have a hail shower, they will charge around like mad things eating lumps of ice.
With wood chips you could of course try a small amount first and see what they make of it.

They will be fine, I have used woodchips for years and years, they love, it, willow is totally edible anyway, they love to kick around in the chips and find bugs and other things to eat, most of our chippings here are spruce, don't forget chickens are woodland creatures rather than of the pasture

Willow is OK but be prepared for very happy chooks as they max out on salicylic acid and the natural natural hormone Indolebutyric Acid (main component in commercial rooting hormones) Personally, I would allow the willow to leach for a month or two before using. Having said that, her the willows along the river are commonly used to provide green forage (important for good rumen function) by lopping branches and allowing the animals to graze them. For me, willows are an invasive species so I remove them totally from my patch.

There are not more than five primary colours, yet in combination they produce more hues than can ever be seen - (Sun Tzu 600BC)

Yes to both of your questions Bonnie
You can easily make rooting "compound" by soaking fresh willow bark or chippings in water for a day or so.
Plus while we're on the subject, make sure that you clear up all the sizeable twigs from your tree, as the reason you can make rooting compound is because willows refuse to die and will take root in a jiffy. Even if you leave a mature log on the ground it will take root.
Aspirin was discovered (I believe) because German midwives in the middle ages gave mothers a fresh willow stick to chew on during childbirth to ease the pain.

we cut some willow down in our field, and then it started raining for two months and we couldn't get the wood up to the shed, I had to literally prise saplings out of the ground when it all started growing again, won't be doing that again in a hurry

I have used willow solution as a rooting stimulant - I used fresh green twigs, poured boiling water over them and let steep for 24 hours. I does work but I have never tried to keep it. The willow is so easy to get that there is really no purpose in trying the store the solution.

There are not more than five primary colours, yet in combination they produce more hues than can ever be seen - (Sun Tzu 600BC)